Abstract

The present invention relates to lithographic apparatuses and processes, and more particularly to tools for optimizing illumination sources and masks for use in lithographic apparatuses and processes. According to certain aspects, the present invention significantly speeds up the convergence of the optimization by allowing direct computation of gradient of the cost function. According to other aspects, the present invention allows for simultaneous optimization of both source and mask, thereby significantly speeding the overall convergence. According to still further aspects, the present invention allows for free-form optimization, without the constraints required by conventional optimization techniques.

IPC Classes  ?

• G03F 1/14 - Originals characterised by structural details, e.g. supports, cover layers, pellicle rings
• G03F 7/20 - ExposureApparatus therefor
• G06F 17/50 - Computer-aided design

Abstract

Methods according to the present invention provide computationally efficient techniques for designing gauge patterns for calibrating a model for use in a simulation process, and which minimize degeneracy between model parameters, and thus maximize pattern coverage for parameter calibration.. More specifically, the present invention relates to methods of designing gauge patterns that achieve complete coverage of parameter variations with minimum number of gauges and corresponding measurements in the calibration of a lithographic process utilized to image a target design having a plurality of features. According to some aspects, a method according to the invention includes transforming the space of model parametric space (based on CD sensitivity or Delta TCCs), then iteratively identifying the direction that is most orthogonal to existing gauges' CD sensitivities in this new space, and determining most sensitive line width/pitch combination with optimal assist feature placement which leads to most sensitive CD changes along that direction in model parametric space.

IPC Classes  ?

• G03F 1/14 - Originals characterised by structural details, e.g. supports, cover layers, pellicle rings
• G03F 7/20 - ExposureApparatus therefor

Abstract

A method of optimizing an illumination pupil shape for a lithographic process 1 comprises identifying a target pattern (206) to be imaged by said lithographic process. It further comprises identifying at least one optimization point (262) in said target pattern and identifying at least one design for manufacturing metric (270) per optimization point. Additionally it comprises selecting a set of illumination source points (274) based on the identified at least one design for manufacturing metric and determining the illumination pupil shape (284) based on the selected set of illumination source points.

IPC Classes  ?

• G03F 7/20 - ExposureApparatus therefor

Abstract

Lithography simulation using a differential model. The differential model describes differences in the imaging characteristics of two scanners related to tunable and non-tunable scanner settings. A model for one of the two scanners is derived by using the model of the other scanner and the differential model. Similarly, a sensitivity model expresses the differences in the imaging characteristics of one scanner related to different scanner settings. Additionally, methods are provided for calibrating the differential model and the sensitivity model by comparison with printing results.

IPC Classes  ?

• G03F 7/20 - ExposureApparatus therefor

Abstract

Systems and methods for tuning photolithographic processes are described. A model of a target scanner is maintained defining sensitivity of the target scanner with reference to a set of tunable parameters. A differential model represents deviations of the target scanner from the reference. The target scanner may be tuned based on the settings of the reference scanner and the differential model. Performance of a family of related scanners may be characterized relative to the performance of a reference scanner. Differential models may include information such as parametric offsets and other differences that may be used to simulate the difference in imaging behavior.

IPC Classes  ?

• G03F 7/20 - ExposureApparatus therefor

Abstract

Methods are disclosed for calibrating a photolithographic system comprising a lens for imaging a reticle design on a substrate. A substrate contour for the reticle design with the lens being maintained within a nominal operation temperature range, called cold lens contour, and at least one substrate heated by light transmission, called hot lens contour, are generated from which a process window is defined. Aberrations induced by a lens manipulator are characterized in a manipulator model and the process window is optimized using the manipulator model. Aberrations are characterized by identifying variations in critical dimensions caused by lens manipulation for a plurality of manipulator settings and by modeling behavior of the manipulator as a relationship between manipulator settings and aberrations. The process window may be optimized by minimizing a cost function for a set of critical locations.

IPC Classes  ?

• G03F 7/20 - ExposureApparatus therefor

Abstract

Methods are disclosed to create efficient model-based Sub-Resolution Assist Features (MB-SRAF). An SRAF guidance map is created, where each design target edge location votes for a given field point on whether a single-pixel SRAF placed on this field point would improve or degrade the aerial image over the process window. In one embodiment, the SRAF guidance map is used to determine SRAF placement rules and/or to fine-tune already-placed SRAFs. The SRAF guidance map can be used directly to place SRAFs in a mask layout. Mask layout data including SRAFs may be generated, wherein the SRAFs are placed according to the SRAF guidance map. The SRAF guidance map can comprise an image in which each pixel value indicates whether the pixel would contribute positively to edge behavior of features in the mask layout if the pixel is included as part of a sub-resolution assist feature.

IPC Classes  ?

• G03F 7/20 - ExposureApparatus therefor